Shell Learning notes-the first day

1. The first line of the program specifies the program that executes the shell

　　#!/bin/sh

#! is used to tell the system that the parameter behind it is the program used to execute the file

2. Output information in the console

echo "Hello Shell"

#!/bin/sh#向控制台输出信息 echo"Hello Shell"

Save, quit!
3, make script executable, need to execute the following command in DOS window

chmod +x FileName

4. Execute script

./helloshell

5, the use of variables

In the shell, variables are not declared and can be used directly (similar to LUA)

Remove variables using dollar sign $

#变量的使用a="I am a variable"echo  $aecho ${a}

The curly braces are used to prevent variables from being adjacent to the string, and what is the indeterminate variable! such as: $numth and ${num}th The former variable named numth variable, the latter takes the variable named Num.

6. Shell Common Commands

File Statistics Command: wc–l filename, wc-w filename, wc-c filename: Calculates the number of file lines, calculates the number of words in the file, calculates the number of characters in the file

File copy: CP sourcefile DestFile
Renaming files or moving files: MV oldname newname
Delete Files: RM file

Search string in file (regular expression supported): grep ' str ' fileName outputs the rows that are searched to the console

Output file contents to screen: Cat FileName

　　

　　

Shell Learning notes-the first day